Environmentally friendly base fluids and methods for making and using same

ABSTRACT

Non-toxic, biodegradable base fluids are disclosed for use in making downhole fluids, where the base fluids include blends of paraffins, olefins, naphthenes, esters, and oxygenates, having low viscosities, having a pale-yellow color, having a flashpoint of &gt;80° C. (175° F.) and have a pour point of about 19° F. Methods for making and using fluids include the base fluids of this invention are also disclosed

RELATED APPLICATIONS

This application is a continuation application and claims the benefit ofand priority to U.S. patent application Ser. No. 12/885,128 filed09/17/2010 (17 Sep. 2010).

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of this invention relate to environmentally friendly basefluids for use in downhole fluid systems and methods for making andusing same.

More particularly, embodiments of the present invention relate toenvironmentally friendly base fluids for use in downhole fluid systemsand methods for making and using same, where the fluids include asolvent system comprising a blend of paraffins, olefins, naphthenes,esters, and oxygenates, where the solvent system has a low viscosity, isa pale-yellow liquid, has a flashpoint >80° C. (175° F.) and has a pourpoint of about 19° F.

2. Description of the Related Art

Employment of base fluids either in the formulation of drilling fluidsfor various drilling operations or as carrier for solutes is commonlypracticed in the oilfield or related industries. Increasingly, morestringent regulations to curtail use of hazardous or toxic chemicals arebeing legislated across the Globe. Consequently, use of some chemicalslike diesel is prohibitive in some regions while there are wide spreadstrict regulations for handling and disposal of several others.

A number of biodegradable mineral or synthetic oil base fluids have beendisclosed in prior art. U.S. Pat, Nos. 6,455,474 and 6,096,690 discloseenvironmentally friendly low temperature base oils and drilling fluidsmade therefrom. U.S. Pat. Nos. 5,189,012 and 4,787,990 disclose lowviscosity blends of poly alpha-olefins (PAO) as a means of reducing thecost of suitable, but expensive and limited in supply PAOs asbiodegradable oils.

While other environmentally friendly or biodegradable solvent systemshave been discribed in the prior art, there is still an immediate andlong felt need in the art for non-hazardous, non-toxic, environmentallyfriendly and biodegradable solvent systems for use as a base fluid indownhole operations or other similar operations.

SUMMARY OF THE INVENTION

Embodiments of this invention provide base fluids for use in downholeoperations, where the base fluids comprise solvent systems includeblends of paraffins, olefins, naphthenes, esters, and oxygenates, havinglow viscosities, having a pale-yellow color, having a flashpoint of >80°C. (175° F.) and having a pour point of about 19° F.

Embodiments of this invention provide drilling fluids including abasefluid of this invention.

Embodiments of this invention provide fracturing fluids including a basefluid of this invention.

Embodiments of this invention provide fluid carriers including a basefluid of this invention.

Embodiments of this invention provide lift fluid including a base fluidof this invention.

Embodiments of this invention provide completion fluids including a basefluid of this invention.

Embodiments of this invention provide stimulating fluids including abase fluid of this invention.

Embodiments of this invention provide methods for drilling, fracturing,completing, stimulating, lifting and/or other downhole operations, wherethe fluids include a blend of paraffins, olefins, naphthenes, esters,and oxygenates, having low viscosities, having a pale-yellow color,having a flashpoint of >80° C. (175° F.) and having a pour point ofabout 19° F.

DEFINITIONS OF TERM USED IN THE INVENTION

The following definitions are provided in order to aid those skilled inthe art in understanding the detailed description of the presentinvention.

The term “fracturing” refers to the process and methods of breaking downa geological formation, i.e. the rock formation around a well bore, bypumping fluid at very high pressures, in order to increase productionrates from a hydrocarbon reservoir. The fracturing methods of thisinvention use otherwise conventional techniques known in the art.

The term “surfactant” refers to a soluble, or partially soluble compoundthat reduces the surface tension of liquids, or reduces inter-facialtension between two liquids, or a liquid and a solid by congregating andorienting itself at these interfaces.

The term “drilling fluids” refers to any fluid that is used during oiland/or gas well drilling operations.

The term “completion fluids” refers to any fluid that is used in oiland/or gas well completion operations.

The term “production fluids” refers to any fluid that is used in oiland/or gas well production operations.

An under-balanced and/or managed pressure drilling fluid means adrilling fluid having a circulating hydrostatic density (pressure) loweror equal to a formation density (pressure). For example, if a knownformation at 10,000 ft (True Vertical Depth—TVD) has a hydrostaticpressure of 5,000 psi or 9.6 lbm/gal, an under-balanced drilling fluidwould have a hydrostatic pressure less than or equal to 9.6 lbm/gal.Most under-balanced and/or managed pressure drilling fluids include atleast a density reduction additive. Other additive many include acorrosion inhibitor, a pH modifier and a shale inhibitor.

The term “foamable” means a composition that when mixed with a gas formsa stable foam.

The term “gpt” means gallons per thousand gallons.

The term “ppt” means pounds per thousand gallons.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have found that new solvent systems can be formulated asbase fluids for use in making drilling fluids, fracturing fluids, fluidcarriers, completion fluids and/or related systems, where the solventsystems include a blend of paraffins, olefins, naphthenes, esters, andoxygenates. The solvent systems have low viscosities, are pale-yellowliquids, have flashpoints of >80° C. (175° F.) and have pour points ofabout 19° F. The inventors have found that the solvent systems of thisinvention maybe used to formulate drilling fluids, completion fluids,fracturing fluids, fluid carriers for other applications, or relatedfluid systems.

The inventors have found that the solvent systems maybe used toformulate completely green systems. Thus, the inventors are able todesign a foamable drilling system including an eco-friendly foamer orplurality of eco-friendly foamers, an eco-friendly defoamer or pluralityof eco-friendly defoamers and an eco-friendly base fluid or plurality ofeco-friendly base fluid. Embodiments of the present invention alsorelated to fracturing slurries with outstanding properties preparedusing the solvent systems of this invention. Unlike other biodegradablesynthetic oils that have been previously disclosed, the solvent systemsof this invention are economical as base fluids having high flashpoints, >80° C. In other embodiments, drilling fluids may be formulatedwith the base fluids of this invention having an extended operatingtemperature range, a temperature range up to about 450° F. The inventorshave found that the fluids of this invention are reusable and possesssuperior properties compared to diesel, while competing oil base fluidsare neither foamable nor give satisfactory foam properties. The presentsolvent systems do not damage seals of downhole tools. The inventorshave found that in fracturing or frac applications, the fluids may beused to formulate slurries that are non-settling and possess high yieldviscosity (lineal gel solution) as compared to known base fluids.Products including the solvent systems of this invention have been fieldtested successfully in an under-balanced drilling operation in Houston,Tex. USA.

Drilling Fluids

Generally, a drilling fluid is used during the drilling of a well.Drilling fluids can be designed for so-called over-balanced drilling (ahydrostatic pressure of the drilling fluid is higher than the porepressure of the formation), under-balanced drilling (a hydrostaticpressure of the drilling fluid is lower than the pore pressure of theformation) or managed pressure drilling, where the hydrostatic pressureof the drilling fluid is managed depending on the nature of the materialthrough which drilling is occurring. Each type of drilling usesdifferent types of drilling fluids. The compositions of this inventionare designed to improve dispersion and stability of the resultingdrilling fluids so that cuttings remain suspended for longer periods oftime or at temperatures up to 450° F.

Embodiments of the present invention relates to drilling fluidsincluding a base fluid composition of this invention, where the basefluid composition includes blends of biodegradable, non-toxic,non-hazardous solvent including biodegradable paraffins, olefins,naphthenes, esters, and oxygenates having a flashpoint ≧80° C. and apour point of about 19° F. The drilling fluids may optionally include adrilling fluid additive package including the additives set forth hereinor mixtures of the additive set forth herein.

Completion Fluids

Embodiments of the present invention relates to completion fluidsincluding a solvent system of this invention as the base fluid, wherethe solvent system of this invention include blends of biodegradable,non-toxic, non-hazardous solvent including biodegradable paraffins,olefins, naphthenes, esters, and oxygenates having a flashpoint ≧80° C.and a pour point of about 19 ° F. The completion fluids may optionallyinclude a completion fluid additive package including the additives setforth herein or mixtures of the additive set forth herein.

Fracturing Fluids

The present invention also relates to methods of fracturing asubterranean formation comprising forming a fracturing fluid including asurfactant system of this invention and pumping the gel or coacervatedown a wellbore, in the presence or absence of a proppant and underpressure sufficient to fracture the formation. Proppants suitable forour invention include all the generally used or generally acceptedproppant materials such as sand, shells, and other hard particulates.The fluid may be used in the absence of conventional brine-formingsalts. Aqueous based gels used for formation fracturing and other welltreatment usually employ guar, cellulose, or gums that depend onchemical bonding and are shear-sensitive.

Embodiments of the present invention relates to fracturing fluidcompositions including a solvent system of this invention as the basefluid, where the solvent system of this invention include blends ofbiodegradable, non-toxic, non-hazardous solvent including biodegradableparaffins, olefins, naphthenes, esters, and oxygenates having aflashpoint ≧80° C. and a pour point of about 19° F. The fracturingfluids may optionally include a fracturing fluid additive packageincluding the additives set forth herein or mixtures of the additive setforth herein. For additional information on fracturing fluid componentsthat may be used with the fracturing fluids of this invention the readeris referred to U.S. Pat. Nos. 7,140,433, 7,517,447, 7,268,100,7,392,847, 7,350,579, 7,712,535, and 7,565,933; and United StatesPublished Applications Nos. 20070032693, 20050137114, 20090250659,20050250666, 20080039345, 20060194700, 20070173414, 20070129257,20080257553, 20090203553, 20070173413, 20080318812, 20080287325,20080314124, 20080269082, 20080197085, 20080257554, 20080251252,20090151959, 20090200033, 20090200027, 20100000795, 20100012901,20090067931, 20080283242, 20100077938, 20100122815, and 20090275488.These applications and patents are incorporated by reference through theoperation of the last paragraph of the specification.

Stimulating Fluids

Embodiments of the present invention relates to stimulating fluidcompositions including a solvent system of this invention as the basefluid, where the solvent system of this invention include blends ofbiodegradable, non-toxic, non-hazardous solvent including biodegradableparaffins, olefins, naphthenes, esters, and oxygenates having aflashpoint 80° C. and a pour point of about 19° F. The stimulatingfluids may optionally include a stimulating fluid additive packageincluding the additives set forth herein or mixtures of the additive setforth herein.

Compositional Ranges

In drilling fluid, stimulating fluid, completion fluid, and lift fluidembodiments, the base fluid compositions of this invention are used in arange between about 1 vol. % and about 100 vol. % (volume, v/volume, v)of the base fluid (the base fluid is the fluid into which all othercomponents of the final fluid are added). In other embodiments, the basefluids are used in a range between about 10 vol. % and about 90 vol. %.In other embodiments, the base fluids are used in a range between about30 and about 70 vol. %. In other embodiments, the base fluids are usedin a range between about 40 vol. % and about 60 vol. %. In otherembodiments, the base fluids make up greater than or equal to about 50vol. % of the base fluid. In other embodiments, the base fluids make upgreater than or equal to about 60 vol. % of the base fluid. In otherembodiments, the base fluids make up greater than or equal to about 70vol. % of the base fluid. In other embodiments, the base fluids make upgreater than or equal to about 80 vol. % of the base fluid. In otherembodiments, the base fluids make up greater than or equal to about 90vol. % of the base fluid. In other embodiments, the base fluids make upabout 100 vol. % of the base fluid.

In fracturing slurries, the base fluid compositions of this inventionare present in a range between about 30 wt. % and about 70 wt. % basedon the weight of the final slurry. In other embodiments, the range isbetween about 30 wt. % and about 60 wt. %. In other embodiments, therange is between about 30 wt. % and about 50 wt. %. In otherembodiments, the range is between about 40 wt. % and about 50 wt. %. Inother embodiments, the base fluid composition is present in an amountless than or equal to about 70 wt. %. In other embodiments, the basefluid composition is present in an amount less than or equal to about 60wt. %. In other embodiments, the base fluid composition is present in anamount less than or equal to about 50 wt. %.

Suitable Reagents Base Fluid Compositions

Suitable base fluid compositions or solvent systems of this inventioninclude, without limitation, blends of biodegradable, non-toxic,non-hazardous solvents including biodegradable paraffins, isoparaffins,olefins, naphthenes, esters, and oxygenates having a flashpoint ≧80° C.and a pour point of about 19° F. Exemplary examples include HF-1000™,ODC®, LPA®, terpenes and mixture of terpenes derived from citrus plantsincluding d-limonenes, orange terpenes, lemon terpenes, grapefruitterpenes, orange oil, lemon oil, other citrus terpenes, other citrusoils, blends of HF-1000™, ODC®, and/or LPA® with the terpenes andmixtures of terpenes or mixtures and combinations thereof.

Foamers

Suitable foaming agents for use in this invention include, withoutlimitation, any foaming agent suitable for foaming hydrocarbon baseddrilling fluids. Exemplary examples of foaming agents include, withoutlimitation, silicone foaming agents such astetra(trimethylsiloxy)silane, fluorinated oligomeric or polymeric foamssuch as fluorinated methacrylic copolymer, or other similar foamingagents capable of producing a foam in a hydrocarbon or oil-baseddrilling fluid or mixtures or combinations thereof. Exemplary examplesof such foaming agents include, without limitation, DC-1250 availablefrom Dow Corning, Zonyl FSG available from DuPont, APFS-16 availablefrom Applied Polymer, A4851 available from Baker Petrolite, Superfoamavailable from Oilfield Solutions, Paratene HFA available fromWoodrising, DVF-880 available from Parasol Chemicals INC., JBR200,JBR300, JBR400, and JBR500 available from Jeneil Biosurfactant Company,Paratene HFA, Paratene HFB, Paratene MFA, Paratene MFB available fromWoodrising Resources Ltd. or mixture or combinations.

Polymers Used in Fracturing Fluids

Suitable polymers for use in this invention include, without limitation,any polymer soluble in the hydrocarbon base fluid. Exemplary polymersinclude, without limitation, a polymer comprising units of one or more(one, two, three, four, five, . . . , as many as desired) polymerizablemono-olefins or di-olefins. Exemplary examples includes, withoutlimitation, polyethylene, polypropylene, polybutylene, or otherpoly-alpha-olefins, polystyrene or othe polyaromatic olefins,polybutadiene, polyisoprene, or other poly-diolefins, or copolymers (apolymer including two or more mono-olefins or di-olefins) or copolymersincluding minor amount of other co-polymerizable monomers such asacrylates (acrylic acid, methyl acrylate, ethyl acrylate, etc.),methacrylates (methacrylic acid, methyl methacrylate, ethylmethacrylate, etc), vinylacetate, maleic anhydride, succinic anhydride,or the like, provided of course that the resulting polymer is soluble inthe hydrocarbon base fluid.

Gelling Agents Using in Fracturing Fluids

Suitable gelling agents for use in this invention include, withoutlimitation, any gelling agent. Exemplary gelling agents includesphosphate esters, ethylene-acrylic acid copolymer, ethylene-methacrylicacid copolymers, ethylene-vinyl acetate copolymers, ethylene-maleicanhydride copolymers, butadiene-methacrylic acid copolymers,ethylene-methacrylic acid copolymers, styrene-butadiene-acrylic acidcopolymers, styrene-butadiene-methacrylic acid copolymers, or othercopolymer including monomers having acid moieties or mixtures orcombinations thereof. Exemplary examples phosphate ester gelling agentsinclude, without limitation, WEC HGA 37, WEC HGA 70, WEC HGA 71, WEC HGA72, WEC HGA 702 or mixtures or combinations thereof, available fromWeatherford International. Other suitable gelling agents include,without limitation, Geltone II available from Baroid, Ken-Gel availablefrom Imco or the like.

Suitable cross-linking agent for use in this invention include, withoutlimitation, any suitable cross-linking agent for use with the gellingagents. Exemplary cross-linking agents include, without limitation, di-and tri-valent metal salts such as calcium salts, magnesium salts,barium salts, copperous salts, cupric salts, ferric salts, aluminumsalts, or mixtures or combinations thereof. Examples cross-linking agentfor use with phosphate esters include, without limitation, WEC HGA 44,WEC HGA 48, WEC HGA 55se, WEC HGA 55s, WEC HGA 61, WEC HGA 65 ormixtures or combinations thereof available from WeatherfordInternational.

Defoamers

Suitable defoaming agents for use in this invention include, withoutlimitation, any defoaming agent capable of reducing the foam height ofthe foamed drilling fluid systems of this invention. Exemplary examplesof defoaming agents are polydimethylsiloxane (Down Corning 200 Fluid™,50 centistokes), low molecular weight alcohols with isopropanol orisopropyl alcohol (IPA) being preferred.

Gases

Suitable gases for foaming the foamable, ionically coupled gelcomposition include, without limitation, nitrogen, carbon dioxide, orany other gas suitable for use in formation fracturing, or mixtures orcombinations thereof.

Corrosion Inhibitors

Suitable corrosion inhibitor for use in this invention include, withoutlimitation: quaternary ammonium salts e.g., chloride, bromides, iodides,dimethylsulfates, diethylsulfates, nitrites, bicarbonates, carbonates,hydroxides, alkoxides, or the like, or mixtures or combinations thereof;salts of nitrogen bases; or mixtures or combinations thereof. Exemplaryquaternary ammonium salts include, without limitation, quaternaryammonium salts from an amine and a quaternarization agent, e.g.,alkylchlorides, alkylbromide, alkyl iodides, alkyl sulfates such asdimethyl sulfate, diethyl sulfate, etc., dihalogenated alkanes such asdichloroethane, dichloropropane, dichloroethyl ether, epichlorohydrinadducts of alcohols, ethoxylates, or the like; or mixtures orcombinations thereof and an amine agent, e.g., alkylpyridines,especially, highly alkylated alkylpyridines, alkyl quinolines, C₆ to C₂₄synthetic tertiary amines, amines derived from natural products such ascoconuts, or the like, dialkylsubstituted methyl amines, amines derivedfrom the reaction of fatty acids or oils and polyamines,amidoimidazolines of DETA and fatty acids, imidazolines ofethylenediamine, imidazolines of diaminocyclohexane, imidazolines ofaminoethylethylenediamine, pyrimidine of propane diamine and alkylatedpropene diamine, oxyalkylated mono and polyamines sufficient to convertall labile hydrogen atoms in the amines to oxygen containing groups, orthe like or mixtures or combinations thereof. Exemplary examples ofsalts ofnitrogen bases, include, without limitation, salts of nitrogenbases derived from a salt, e.g.: C₁ to C₈ monocarboxylic acids such asformic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid,hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, orthe like; C₂ to C₁₂ dicarboxylic acids, C₂ to C₁₂ unsaturated carboxylicacids and anhydrides, or the like; polyacids such as diglycolic acid,aspartic acid, citric acid, or the like; hydroxy acids such as lacticacid, itaconic acid, or the like; aryl and hydroxy aryl acids; naturallyor synthetic amino acids; thioacids such as thioglycolic acid (TGA);free acid forms of phosphoric acid derivatives of glycol, ethoxylates,ethoxylated amine, or the like, and aminosulfonic acids; or mixtures orcombinations thereof and an amine, e.g.: high molecular weight fattyacid amines such as cocoamine, tallow amines, or the like; oxyalkylatedfatty acid amines; high molecular weight fatty acid polyamines (di, tri,tetra, or higher); oxyalkylated fatty acid polyamines; amino amides suchas reaction products of carboxylic acid with polyamines where theequivalents of carboxylic acid is less than the equivalents of reactiveamines and oxyalkylated derivatives thereof; fatty acid pyrimidines;monoimidazolines of EDA, DETA or higher ethylene amines, hexamethylenediamine (HMDA), tetramethylenediamine (TMDA), and higher analogsthereof; bisimidazolines, imidazolines of mono and polyorganic acids;oxazolines derived from monoethanol amine and fatty acids or oils, fattyacid ether amines, mono and bis amides of aminoethylpiperazine; GAA andTGA salts of the reaction products of crude tall oil or distilled talloil with diethylene triamine; GAA and TGA salts of reaction products ofdimer acids with mixtures of poly amines such as TMDA, HMDA and1,2-diaminocyclohexane; TGA salt of imidazoline derived from DETA withtall oil fatty acids or soy bean oil, canola oil, or the like; ormixtures or combinations thereof.

Other Additives

The drilling fluids of this invention can also include other additivesas well such as scale inhibitors, carbon dioxide control additives,paraffin control additives, oxygen control additives, or otheradditives.

Scale Control

Suitable additives for Scale Control and useful in the compositions ofthis invention include, without limitation: Chelating agents, e.g., Na⁺,K⁻ or NH₄ ⁺, K⁺ or NH₄ ⁻ salts of NTA; Na⁺, K⁺ or NH₄ ⁺ salts ofErythorbic acid; Na³⁰ , K⁺ or NH₄ ⁺ salts of thioglycolic acid (TGA);Na⁺, K⁺ or NH₄ ⁺ salts of Hydroxy acetic acid; Na⁺, K⁺ or NH₄ ⁺ salts ofCitric acid; Na⁺, K⁺ or NH₄ ⁺ salts of Tartaric acid or other similarsalts or mixtures or combinations thereof. Suitable additives that workon threshold effects, sequestrants, include, without limitation:Phosphates, e.g., sodium hexamethylphosphate, linear phosphate salts,salts of polyphosphoric acid, Phosphonates, e.g., nonionic such as HEDP(hydroxyethylidene diphosphoric acid), PBTC (phosphoisobutane,tricarboxylic acid), Amino phosphonates of: MEA (monoethanolamine), NH₃,EDA (ethylene diamine), Bishydroxyethylene diamine, Bisaminoethylether,DETA (diethylenetriamine), HMDA (hexamethylene diamine), Hyperhomologues and isomers of HMDA, Polyamines of EDA and DETA,Diglycolamine and homologues, or similar polyamines or mixtures orcombinations thereof; Phosphate esters, e.g., polyphosphoric acid estersor phosphorus pentoxide (P₂O₅) esters of: alkanol amines such as MEA,DEA, triethanol amine (TEA), Bishydroxyethylethylene diamine;ethoxylated alcohols, glycerin, glycols such as EG (ethylene glycol),propylene glycol, butylene glycol, hexylene glycol, trimethylol propane,pentaerythritol, neopentyl glycol or the like; Tris & Tetra hydroxyamines; ethoxylated alkyl phenols (limited use due to toxicityproblems), Ethoxylated amines such as monoamines such as MDEA and higheramines from 2 to 24 carbons atoms, diamines 2 to 24 carbons carbonatoms, or the like; Polymers, e.g., homopolymers of aspartic acid,soluble homopolymers of acrylic acid, copolymers of acrylic acid andmethacrylic acid, terpolymers of acylates, AMPS, etc., hydrolyzedpolyacrylamides, poly malic anhydride (PMA); or the like; or mixtures orcombinations thereof.

Carbon Dioxide Neutralization

Suitable additives for CO₂ neutralization and for use in thecompositions of this invention include, without limitation, MEA, DEA,isopropylamine, cyclohexylamine, morpholine, diamines,dimethylaminopropylamine (DMAPA), ethylene diamine, methoxy propylamine(MOPA), dimethylethanol amine, methyldiethanolamine (MDEA) & oligomers,imidazolines of EDA and homologues and higher adducts, imidazolines ofaminoethylethanolamine (AEEA), aminoethylpiperazine, aminoethylethanolamine, di-isopropanol amine, DOW AMP-90™, Angus AMP-95, dialkylamines(of methyl, ethyl, isopropyl), mono alkylamines (methyl, ethyl,isopropyl), trialkyl amines (methyl, ethyl, isopropyl),bishydroxyethylethylene diamine (THEED), or the like or mixtures orcombinations thereof.

Paraffin Control

Suitable additives for Paraffin Removal, Dispersion, and/or paraffinCrystal Distribution include, without limitation: Cellosolves availablefrom DOW Chemicals Company; Cellosolve acetates; Ketones; Acetate andFormate salts and esters; surfactants composed of ethoxylated orpropoxylated alcohols, alkyl phenols, and/or amines; methylesters suchas coconate, laurate, soyate or other naturally occurring methylestersof fatty acids; sulfonated methylesters such as sulfonated coconate,sulfonated laurate, sulfonated soyate or other sulfonated naturallyoccurring methylesters of fatty acids; low molecular weight quaternaryammonium chlorides of coconut oils soy oils or C₁₀ to C₂₄ amines ormonohalogenated alkyl and aryl chlorides; quanternary ammonium saltscomposed of disubstituted (e.g., dicoco, etc.) and lower molecularweight halogenated alkyl and/or aryl chlorides; gemini quaternary saltsof dialkyl (methyl, ethyl, propyl, mixed, etc.) tertiary amines anddihalogenated ethanes, propanes, etc. or dihalogenated ethers such asdichloroethyl ether (DCEE), or the like; gemini quaternary salts ofalkyl amines or amidopropyl amines, such as cocoamidopropyldimethyl, bisquaternary ammonium salts of DCEE; or mixtures or combinations thereof.Suitable alcohols used in preparation of the surfactants include,without limitation, linear or branched alcohols, specially mixtures ofalcohols reacted with ethylene oxide, propylene oxide or higheralkyleneoxide, where the resulting surfactants have a range of HLBs.Suitable alkylphenols used in preparation of the surfactants include,without limitation, nonylphenol, decylphenol, dodecylphenol or otheralkylphenols where the alkyl group has between about 4 and about 30carbon atoms. Suitable amines used in preparation of the surfactantsinclude, without limitation, ethylene diamine (EDA), diethylenetriamine(DETA), or other polyamines. Exemplary examples include Quadrols,Tetrols, Pentrols available from BASF. Suitable alkanolamines include,without limitation, monoethanolamine (MEA), diethanolamine (DEA),reactions products of MEA and/or DEA with coconut oils and acids.

Oxygen Control

The introduction of water downhole often is accompanied by an increasein the oxygen content of downhole fluids due to oxygen dissolved in theintroduced water. Thus, the materials introduced downhole must work inoxygen environments or must work sufficiently well until the oxygencontent has been depleted by natural reactions. For system that cannottolerate oxygen, then oxygen must be removed or controlled in anymaterial introduced downhole. The problem is exacerbated during thewinter when the injected materials include winterizers such as water,alcohols, glycols, Cellosolves, formates, acetates, or the like andbecause oxygen solubility is higher to a range of about 14-15 ppm invery cold water. Oxygen can also increase corrosion and scaling. In CCT(capillary coiled tubing) applications using dilute solutions, theinjected solutions result in injecting an oxidizing environment (O₂)into a reducing environment (CO₂, H₂S, organic acids, etc.).

Options for controlling oxygen content includes: (1) de-aeration of thefluid prior to downhole injection, (2) addition of normal sulfides toproduct sulfur oxides, but such sulfur oxides can accelerate acid attackon metal surfaces, (3) addition of erythorbates, ascorbates,diethylhydroxyamine or other oxygen reactive compounds that are added tothe fluid prior to downhole injection; and (4) addition of corrosioninhibitors or metal passivation agents such as potassium (alkali) saltsof esters of glycols, polyhydric alcohol ethyloxylates or other similarcorrosion inhibitors. Exemplary examples of oxygen and corrosioninhibiting agents include mixtures of tetramethylene diamines,hexamethylene diamines, 1,2-diaminecyclohexane, amine heads, or reactionproducts of such amines with partial molar equivalents of aldehydes.Other oxygen control agents include salicylic and benzoic amides ofpolyamines, used especially in alkaline conditions, short chainacetylene diols or similar compounds, phosphate esters, borateglycerols, urea and thiourea salts ofbisoxalidines or other compoundthat either absorb oxygen, react with oxygen or otherwise reduce oreliminate oxygen.

Salt Inhibitors

Suitable salt inhibitors for use in the fluids of this inventioninclude, without limitation, Na Minus Nitrilotriacetamide available fromClearwater International, LLC of Houston, Tex.

Foam Characteristics

Generally, the foamable hydrocarbon drilling fluid systems of thisinvention from an initial fluid amount of 100 mL, will produce a foamhaving a foam height of at least 150 mL and a half life of at least 2minutes. In particular, the produced foam will have a foam heightbetween about least 150 mL and about 500 mL and a half life betweenabout 2 minutes and 15 minutes depending on the application and theexact formulation of the hydrocarbon fluid of this invention. Thestability or half life and foam height of the produced foam iscontrolled by the amount and type of the viscosifying agents in thecomposition, by the amount and type of the foaming agents in thecomposition, by the amount of gas and type of gas in the composition, bythe temperature of the composition and by the pressure of thecomposition. Generally, increasing the amount of the viscosifying agentsand/or foaming agents leads to increased foam height and foam stability.Generally, the viscosifying agents increase the stability more than thefoam height, while the foaming agents increase the foam height. Ofcourse, the foam height is also directly proportional to the amount andtype of gas dissolved or absorbed in the fluid.

EXPERIMENTS OF THE INVENTION Introduction

The inventors designed the present solvent systems to be eco-friendlyand biodegradable and at the same time be capable of maintaining shaleintegrity to insure that the fluids do not result in adverse shaleswelling problems producing shale instability. Indeed, the inventorsdeveloped oil-based foam systems using the solvent systems of thisinvention to actualize the benefits of oil-based fluids for use indrilling through active formations. The solvent systems of thisinvention provide a low cost base fluid for preparing oil-based foamsystems. The solvent systems of this invention are capable of achievingsavings of over a million dollars in casing operations alone. Theinventors have studied the solvent systems of this invention in foameddrilling fluid formulations and in fracturing slurry formulations.

Conclusions

The present solvent systems are suitable base fluids for oil-basedfoamed drilling fluids and for fracturing slurries. The inventors havesuccessfully prepared foamed drilling fluid systems using the solventsystems of this invention as base fluids in drilling operation. Thesolvent systems of this invention are suitable in the preparation ofhigh flash point, environmentally benign fluids that are non-settlingAnd Have High Yield Viscosities In Fracturing Slurry Systems.

Result & Discussion

Foamed drilling systems based on the solvent systems of this inventionwere formulated, where the solvents systems of this invention form acontinuous phase. The foamed drilling systems had desirable foamproperties and were successfully field tested. The foamed drillingsystems are not only highly thermally stable due to the thermalstability of the base fluid comprising a solvent system of thisinvention, they are also recyclable in a foam-defoam-foam process. Infracturing applications, the solvent systems of this invention can beused to prepare biodegradable, high flash point, fracturing slurries,which are non-settling and possess high viscosities.

Formulations

a. Foam Systems

Often, foamers are employed in drilling operations in liquid state; sayfor ease of handing, for reducing column weight or for forming lightweight drilling fluids. While the main surface active chemicals of thesesystems may not be toxic (e.g., saccharide surfactants), use ofnon-environmentally benign solvents like alcohols, xylenes, toluene andethers are common. Because of the negative effects of such chemicals onthe ecosystem, it is always desirable to use non-toxic, biodegradablesolvent systems or makeup fluids based on non-toxic, biodegradablesolvent systems. The solvent systems of this invention were employed toformulate surfactant systems to prepare downhole foamed fluid systemsthat are non-toxic, biodegradable and non-settling. The downhole fluidsystems include non-toxic, biodegradable drilling fluids, completionfluids, fracturing fluids, stimulating fluids, lift fluids, enhancingfluids, production fluids, or other similar fluids.

The inventors have found that the solvent systems of this invention arecapable of forming foamed drilling fluids including variousconcentrations of active foaming agents such as fluoroaliphaticpolymeric esters foaming agents, silicon foaming agents, or mixtures andcombinations thereof. The resulting formulations are then useable indownhole operations such as drilling, fracturing, stimulating, lifting,stimulating, enhancing, or other similar downhole operations, where thefluids are benign or substantially benign (having little adverse affecton the environment). Of great environmental appeal is suitability of thesolvent systems of this invention as a substitute for diesel or othercommonly used continuous phase solvents in downhole operations includingdrilling operations using oil-based drilling fluids, where the otherdrilling fluid systems might be non-economic, toxic and/ornon-biodegradable. The inventors have demonstrated that highly stabledrilling fluid systems may be formulated using the solvent systems ofthis invention as the base fluid for the drilling fluid systems.

EXAMPLE 1

The present example illustrates the use of HF-1000™ as anon-toxic,biodegradable solvent system designated SS to prepare foamed drillingfluids. The SS based drilling fluids are compared to drilling fluidsprepared with Red Diesel.

Table 1 tabulates the foam properties of drilling fluids prepare usingSS and Red Diesel.

TABLE 1 Comparison of Diesel and SS as Base Fluids in Foam Systems SeaHeat Foam Base Water KCl Stability Height Half Life Ave Fan 35A FluidConc. (3.5%) (3.0%) Condensate Crude Oil (24 hr) (mL) (min:sec) Recycle(Pv, Yp) Red 1.0% F1^(a) 170 4:00 200/4:15 11, 2 Diesel 10% 170 4:00 20%170 4:00 30% 170 4:00  5% 160 4:00 10% 160 4:00 20% 160 4:00  5% 1604:00 10% 170 4:00 20% 180 4:00 10% 160 4:00 20% 160 4:00 450° F. 1604:00 SS   1% F1^(a) 170 4:00 200/4:15  5, 2 10% 170 2:45 20% 160 2:4030% 160 2:30  5% 170 3:00 10% 160 2:45 20% 160 2:30  5% 170 3:00 10% 1602:40 20% 160 2:30 10% 180 3:00 20% 190 3:00 450° F. 160 3:40 ^(a)F1 isOleoFoam ™C and OleoVis ™HT both available from Weatherford.

The foam properties of the foamed drilling fluid systems shown in Table1 for Red Diesel and SS are quite comparable and are sufficient forfoamed drilling applications. Thus, SS is a robust and versatile solventsystem for use as a base fluid for foamed drilling fluid system.

b. Slurry Systems

Embodiments of this invention relate to slurries compositions orformulations prepared using SS as the base solvent system, where thecompositions decrease settling of particulate materials in the slurriesand increase hydration properties of hydratable particulate materials inthe slurries. In slurry system development, two recurring concerns arebiodegradability and flammability of the base fluid. The solvent systemsof this invention were found to satisfactorily and sufficiently addressboth of these concerns.

EXAMPLE 2

Two slurry formulations were prepared using SS and Conosol 145 (acommercially available base oil from Calumet Specialty Partners, USA)formulated independently as base fluid according to the formulationstabulated in Table 2.

TABLE 2 Slurry Composition Component Concentration (%) Base oil (g)47.91 Winterizing Agent (Arlacel 83) 0.48 Clay (Bentone 150) 2.00Surfactant Blend (Suspend Aid) 0.98 Polymer (WGA 15) 48.63 Total 100.00

The slurries were tested and the test results are tabulated in Table 3.

TABLE 3 SS and Conosol 145 Based Slurries Conosol Slurry Property 145Based Slurry SS Based Slurry Specific Gravity (25° C.) 1.048-1.062   1.059 Flashpoint (° F.) >152 >212  Pour point (° F.) 0 44 DynamicSettling^(a) 2% <1% Static Settling^(b) 1% <1% Hydration Yield (72° F.,cP) 42 46 Slurry Viscosity (72° F., cP) 320-520  854^(c ) ^(a)%, 72° F.,72 hr ^(b)%, 105° F., 72 hr ^(c)(R1:B1 @ 511/s)

The data of Table 3 show physical properties of the slurries preparedusing SS and Conosol 145. The data in Table 3 exemplify desirable andsuperior properties of slurries based on SS as compared to slurriesbased on Conosol 145. The data show that the SS based slurry has reducedsettling (<1%) for WGA 15 polymers (WGA 15 is available fromWeatherford) in the SS based slurry as compared to the Conosol 145 baseslurry (2.0%) for WGA 15 polymers in the Conosol 145 base slurry. Incertain embodiments, the SS slurries of this invention may be formulatedhaving a flash point temperature higher than 212° F. In otherembodiments, higher yield viscosity slurries of the lineal gel solutionare obtainable with SS than with Conosol 145.

All references cited herein are incorporated by reference. Although theinvention has been disclosed with reference to its preferredembodiments, from reading this description those of skill in the art mayappreciate changes and modification that may be made which do not departfrom the scope and spirit of the invention as described above andclaimed hereafter.

We claim:
 1. A method for using a downhole fluid comprising the step: drilling an oil or gas well, fracturing a formation, completing an oil or gas well, stimulating an oil or gas well, producing an oil or gas well, or lifting fluid from an oil or gas well using a downhole fluid comprising: a base fluid comprising a blend of biodegradable, non-toxic, non-hazardous solvents including biodegradable isoparaffins, terpenes, or mixtures and combinations thereof, and a drilling, fracturing, completing, stimulating, producing, or lifting additive package, where the base fluid has a low viscosity, has a flashpoint of >80° C. (175° F.), has a pour point of about 19 ° F. (−7.2° C.), is non-toxic, is biodegradable, and has an operating temperature range up to about 450° F.
 2. The method of claim 1, wherein the drilling, completing, producing or lifting additive package comprises at least a foaming agent and a gas in concentrations sufficient to produce a foamed drilling fluid having a foam height of at least 150 mL and a half life of at least 2 minutes.
 3. The method of claim 2, wherein the base fluid comprises blends of isoparaffins and terpenes.
 4. The method of claim 3, wherein the terpenes comprise d-limonenes, orange terpenes, lemon terpenes, grapefruit terpenes, orange oil, lemon oil, other citrus terpenes, other citrus oils, or mixtures and combinations thereof.
 5. The method of claim 2, wherein the base fluid comprises blends of isoparaffins and mixtures of terpenes.
 6. The method of claim 5, wherein the terpenes comprise d-limonenes, orange terpenes, lemon terpenes, grapefruit terpenes, orange oil, lemon oil, other citrus terpenes, other citrus oils, or mixtures and combinations thereof.
 7. The composition of claim 2, wherein the base fluid comprises blends of isoparaffins.
 8. The composition of claim 1, wherein the completing, stimulating, producing, or lifting additive package include polymers and gelling agents, where the gelled compositions have increased viscosity.
 9. A method for drilling comprising the step: drilling an oil or gas well with a drilling fluid comprising: a base fluid comprising a blend of biodegradable, non-toxic, non-hazardous solvents including biodegradable isoparaffins, terpenes, or mixtures and combinations thereof, and a drilling fluid additive package comprising at least a foaming agent and a gas in concentrations sufficient to produce a foamed downhole fluid having a foam height of at least 150 mL and a half life of at least 2 minutes, where the additive package comprises at least a foaming agent and a gas in concentrations sufficient to produce a foamed drilling fluid having a foam height of at least 150 mL and a half life of at least 2 minutes, and where the base fluid has a low viscosity, has a flashpoint of >80° C. (175° F.), has a pour point of about 19° F. (−7.2° C.), is non-toxic, is biodegradable, and has an operating temperature range up to about 450° F.
 10. The method of claim 9, wherein the base fluid comprises blends of isoparaffins and terpenes.
 11. The method of claim 10, wherein the terpenes comprise d-limonenes, orange terpenes, lemon terpenes, grapefruit terpenes, orange oil, lemon oil, other citrus terpenes, other citrus oils, or mixtures and combinations thereof.
 12. The method of claim 10, wherein the base fluid comprises blends of isoparaffins and mixtures of terpenes.
 13. The method of claim 12, wherein the terpenes comprise d-limonenes, orange terpenes, lemon terpenes, grapefruit terpenes, orange oil, lemon oil, other citrus terpenes, other citrus oils, or mixtures and combinations thereof.
 14. The composition of claim 10, wherein the base fluid comprises blends of isoparaffins.
 15. A method for fracturing comprising the step: fracturing an oil or gas well with a fracturing slurry comprising: the base fluid, and a fracturing fluid additive package comprising at least a clay, a surfactant blend, a polymer, and a winterizing agent, where the base fluid has a low viscosity, has a flashpoint of >80° C. (175° F.), has a pour point of about 19° F. (−7.2° C.), is non-toxic, is biodegradable, and has an operating temperature range up to about 450° F.
 16. The method of claim 15, wherein the fracturing slurry further includes a foaming agent and a gas in concentrations sufficient to produce a foamed drilling fluid having a foam height of at least 150 mL and a half life of at least 2 minutes.
 17. The method of claim 15, wherein the base fluid comprises blends of isoparaffins and terpenes.
 18. The method of claim 17, wherein the terpenes comprise d-limonenes, orange terpenes, lemon terpenes, grapefruit terpenes, orange oil, lemon oil, other citrus terpenes, other citrus oils, or mixtures and combinations thereof.
 19. The method of claim 17, wherein the base fluid comprises blends of isoparaffins and mixtures of terpenes.
 20. The method of claim 19, wherein the terpenes comprise d-limonenes, orange terpenes, lemon terpenes, grapefruit terpenes, orange oil, lemon oil, other citrus terpenes, other citrus oils, or mixtures and combinations thereof.
 21. The composition of claim 17, wherein the base fluid comprises blends of isoparaffins. 